-Keep the characters, but have Bartromy and Jihl join the party to give you extra characters and thus interesting character dynamics. I think both could provide cool interactions, particularly with Hope, Snow, and Sazh.
-Change the Paradigm system by having a FFIX leveling system, which equipment determines skills you can equip/learn. And insetad of roles, give each character two unique jobs to change to how you see fit. As a result, you can have them change on the fly, but you have to set up your paradigms in a way where all characters change to the other class. So, say you have Lightning with Paladin, Snow with Monk, and Sazh with Green Mage as your default set-up. You have to change all three characters' classes, requiring to you to put more strategy in your set-up.
I propose these class settings...
Lightning-Paladin/Dark Knight
Snow-Monk/Berserker
Sazh-Green Mage/Gunner
Vanille-Black Mage/Thief
Hope-White Mage/Chemist
Fang-Dragoon/Trainer
Jihl (she would use a rod)-Blue Mage/Gambler
Bartromy (he'd use a rifle)-Red Mage/Alchemist
-Make the whole l'Cie hunt not so highly broadcated, that way you could incorporate towns and more laidback moments but still require the party to maybe have to hurry.
-Remove Auto-Battle and give me control of all three characters. Other than that, give me more combat options, like maybe Front Row and Back Row choices (That could be change along with Paradigms) and more spells, skills, and items.
-Better writing. Oh, and make a more interesting villain.
-Explore the lore more and let us explore Pulse's history more.
-Give us a really shocking plot twist. Kill of a character or something but make it unexpected.
-Expand the weapon crafting system. Make us seek to create certain weapons to learn certain skills, requiring greater long-term planning.
-Make Nautilus like Gold Saucer.
-Allow us to explore all of Cocoon. Cocoon could've been really cool and futuristic but they ruined it by keeping us confined.
-More siequests. Chocobo Treasure Hunting could be loads of fun.
-And for the love of god, get rid of the Codex and just tell a straightforward narrative without making us do homework.
So, thoughts? How would you change FFXIII?